AIIMS forensic head Sudhir Gupta in 2014 had said that Polonium-210 or Po-210 might have been used to kill Sunanda Pushkar.

The latest FBI report confirms findings of AIIMS post-mortem report given by Dr Sudhir Gupta in 2014 in the Sunanda Pushkar case. The report says Sunanda died due to poisoning - caused by Polonimum-210 or Po-210.

The Delhi Police sources on Friday said the report is almost on the same lines and in their report they have detected one more poison which is dangerous to heart.

The AIIMS doctors' body which was asked to give its opinion on FBI viscera report on the possible cause of Sunanda Pushkar's death on Friday said overdose of anti-anxiety drug Alprazolam killed her. The AIIMS report also slammed the FSL and CFSL over their failure to detect poisioning in Sunanda's body.

However, AIIMS forensic head Sudhir Gupta in 2014 had said that Polonium-210 or Po-210 might have been used to kill Sunanda. Po-210 is a rare and highly radioactive isotope that is not easily available and extremely hard to detect.

The Special Investigation Team (SIT), which is probing the Sunanda Pushkar case, may question Sunanda's husband and Congress leader Shashi Tharoor once again in the case.

Delhi Police chief BS Bassi said, "The medical board report has been received and merits shall be ensured in the case. "I can say with certainty that the death was not natural."

Amid conflicting information about what caused her death, the FBI was asked to help analyse Sunanda viscera samples.

Sunanda's samples were sent to the US for testing after traces of radioactive isotopes were found in her body during the post-mortem examination. The eight-page FBI report, received around nine months after the samples were sent for examination, had ruled out radiation poisoning in Sunanda's case.

The investigators have so far conducted polygraph test on six persons, all prime witnesses in the case, including Tharoors' domestic help Narayan Singh, driver Bajrangi and Sanjay Dewan, a close friend of the couple. Tharoor was not subjected to the test but was questioned.

Sunanda, who married Tharoor in 2010, was found dead under mysterious circumstances inside a room at the Leela Palace Hotel in Delhi on January 17, 2014. Police registered a murder case on January 1, 2015.

Prior to her death, Sunanda was embroiled in a spat with Pakistani journalist Mehr Tarar, whom she accused of stalking her husband.